PURINE ENZYME-ACTIVITIES IN RECENT-ONSET RHEUMATOID-ARTHRITIS - ARE THERE DIFFERENCES BETWEEN PATIENTS AND HEALTHY CONTROLS

Objective-Purine enzyme activities may predict the effectiveness of az athioprine treatment and be associated with increased deaths from infe ctious diseases. In rheumatoid arthritis, patients show variable respo nses to azathioprine and a higher percentage of death is caused by inf ections. The aim of the study was to investigate possible rheumatoid a rthritis associated abnormalities of purine enzyme activities by measu ring several of these enzymes in patients with recent onset rheumatoid arthritis before treatment with disease modifying antirheumatic drugs or prednisone. Methods-23 patients with recent onset rheumatoid arthr itis and 28 healthy controls were studied. Activities of the enzymes 5 '-nucleotidase, purine nucleoside phosphorylase (PNP), hypoxanthine gu anine phosphoribosyltransferase (HGPRT), and thiopurine methyltransfer ase (TPMT) were measured. Assessment of disease activity and blood sam pling for routine measurements and HLA typing were done simultaneously . Results-Purine enzyme activities did not differ between patients and healthy controls. Enzyme activities had no significant relations with indices of disease activity or rheumatoid factor titre or with the rh eumatoid arthritis associated HLA types. Activity of 5'nucleotidase de creased with age (P less than or equal to 0.05) and was lower by about 27% (P = 0.007) in males than in females.Conclusions-In rheumatoid ar thritis patients, neither the variability in azathioprine effectivenes s nor the increased death rate from infections can be explained by pre -existing abnormalities in the activities of the purine enzymes 5'-nuc leotidase, PNP, HGPRT, or TPMT at an early stage of the disease, befor e disease modifying antirheumatic drugs or prednisone treatment. Besid es adjustment for age, results of studies involving purine 5'nucleotid ase activity should also be adjusted for sex.